Used for loading and unloading a workpiece such as a semiconductor wafer to/from a cassette is a multi-joint industrial robot, in which multiple arms are connected each other so as to be rotatable and carry out expanding/folding motion by making use of transmission of turning power from a turning drive power supply. Then, a workpiece transfer system includes a plurality of cassettes in which workpieces are stored, a workpiece processing apparatus, and the multi-joint industrial robot. A conventional workpiece transfer system (Refer to Patent Document 1 for example) is described in detail with reference to FIG. 5.
As shown in FIG. 5, the conventional workpiece transfer system includes: a multi-joint industrial robot 100, a workpiece processing apparatus 200, and a plurality of cassettes (e.g., cassettes C1, C2, C3) in which a workpiece 301 through a workpiece 303 are stored. Workpieces are mounted onto shelves of the cassettes, and the multi-joint industrial robot 100 loads and unloads a workpiece to/from each shelf of the cassette. On this occasion, assumed as the cassette for example is a so-called ‘FOUP’ (Front-Opening Unified Pod) type cassette, a cassette-integrated front-opening unified pod for transfer operation and storage, specified in item E47.1 of SEMI (Semiconductor Equipment and Materials International) standards. The plurality of cassettes are placed in parallel at regular intervals. The multi-joint industrial robot 100 includes: a hand part 101, an arm part 102, an arm-side link part 103, a base-side link part 104, and a base 105; and the multi-joint industrial robot 100 is prepared to carry out, for example, taking the workpiece 303 out of a cassette (the cassette 3) and transferring the workpiece 303 to the workpiece processing apparatus 200.
The multi-joint industrial robot 100 is located at a middle position between the workpiece processing apparatus 200 and the plurality of cassettes (cassettes C1, C2, C3). More concretely to describe; where a straight line connecting each center of the workpiece 301 through the workpiece 303 stored in the plurality of cassettes is defined as a straight line S1 while another straight line included at the rear side of the workpiece processing apparatus 200 and being parallel with the straight line S1 is defined as a straight line S2, the multi-joint industrial robot 100 is located on a straight line S3 composed of points that are equally distant from the straight line 1 and the straight line S2.
On the occasion of the workpiece transfer system shown in FIG. 5, a 3-‘FOUP’ unit dealing with the 3 cassettes that store 3 workpieces, i.e., the workpiece 301 through the workpiece 303, is employed. When a 4-‘FOUP’ unit dealing with the 4 cassettes is employed instead; all or at least a part of the arm part 102, the arm-side link part 103, and the base-side link part 104 needs to be elongated in their length. In a case dealing with 5 cassettes or more, such elongation in those parts is also required.
[Patent Document 1]
Japanese Unexamined Patent Publication (Kokai) No. JP2006-289555
When all or a part of the arm part 102, the arm-side link part 103, and the base-side link part 104 is elongated in their length, it becomes possible to access in a further distance in the X-direction on FIG. 5 (to enable dealing with 4-‘FOUP’ unit). Unfortunately in this case, an interference area of the industrial robot is enlarged in the Y-direction on FIG. 5. Accordingly, an entire section of the multi-joint industrial robot 100 and an entire system of the workpiece transfer system as well are enlarged (so that the industrial robot requires a wide installation space). In the case that FIG. 5 describes for example; the interference area having the dimension ‘M’ in the Y-direction on FIG. 5, i.e., an area required for work of the industrial robot (where the industrial robot can carry out its work with neither interfering with the cassettes in which the workpieces are stored nor interfering with the workpiece processing apparatus), becomes enlarged and eventually the dimension ‘N’ also becomes greater.
At least an embodiment of the present invention has been materialized from the viewpoint of the problem described above. Namely, at least an embodiment of the present invention provides a workpiece transfer system that prevents the system itself as a whole from becoming larger so as to enable space-saving of the system even when the system deals with numbers of cassettes.